The present invention relates generally to fire safety, and more particularly to a flame indicator for a mobile applicator for marking pavement with thermoplastics.
Alkyd and hydrocarbon thermoplastics are commonly used to mark pavement surfaces with visible lines and symbols such as lane dividers and guide lines. In particular, thermoplastics provide a durable alternative to pavement painting, and are commonly used to mark street intersections, parking lots, and other high-traffic pavement surfaces from which paint would quickly wear away.
Thermoplastics are conventionally applied to pavement surfaces using a mobile applicator comprising a heated reservoir or kettle, and an application screed die. Melted thermoplastic is dispensed from the kettle at a controlled rate and applied in a thin layer atop pavement surfaces with the screed die. Some applicators further comprise secondary burners which heat secondary reservoirs or screed die. Many applicators burn pressurized gas, such as propane and butane, at secondary burners and to heat applicator kettles. Manually driven and self-powered applicators are both relatively common, and some applicators can be attached to and driven by vehicles.
Burners for thermoplastic melters and applicators typically operate by releasing a jet of pressurized combustible gas. When lit, this gas acts as a torch which is directed at components to be heated, such as the applicator kettle or screed die. Unlit jets of pressurized gas can constitute a serious safety hazard, rapidly releasing dangerous quantities of combustible gas into the air. Flames on gas burners can be pale and difficult to see, particularly in bright light, making it difficult for mobile applicator operators to ascertain whether a gas jet is lit (and therefore safe) or unlit (and therefore potentially dangerous).